The invention relates to an electromagnetic hydraulic valve with a magnetic armature, which is guided in an armature guide so that it can move longitudinally and which actuates a valve push rod running in a valve housing. This valve push rod controls the connection between connection openings constructed in the valve housing for hydraulic medium by placing the valve push rod in active connection with one or more sealing bodies that correspond to one or more sealing sleeves supported on the valve housing, wherein the hydraulic valve has means for separating sediment particles.
Hydraulic valves, which have means for separating sediment particles from the hydraulic medium for guaranteeing continuous functionality of the hydraulic valves themselves or components running downstream, are known in the state of the art. These sediment particles are led into the hydraulic valve as suspended particles in the hydraulic medium and originate, on one hand, from so-called residual sediment, which accumulates during production, for example, of an internal combustion engine, predominantly in the form of metallic particles and which can also not be completely removed through complicated cleaning measures. On the other hand, these sediment particles are produced through continuous rubbing of moving components during the operation of the internal combustion engine. Thus, the functionality, in particular, of horizontally installed hydraulic valves, can be endangered due to the excessive penetration of sediment particles between the magnetic armature and its armature guide. The resulting tightness of the magnetic armature as a rule leads to a considerable negative effect on the switching dynamics of the hydraulic valve and manifests itself in a reduced and/or greatly fluctuating gradient of the hydraulic medium pressure. In the extreme case, sediment particles led into the armature guide cause a complete failure of the hydraulic valve due to a locking magnetic armature.
For example, in DE 196 31 631 A1, which is considered to be a class-defining patent, an electromagnetic hydraulic valve is provided, whose pressure connection features a sieve filter for the inlet-side separation of sediment particles. This method, however, is associated with a few disadvantages, which are explained below.
First, it is not taken into account that sediment residue in the hydraulic valve itself due to production, as well as sediment particles produced by the operating interaction between moving components in the hydraulic valve, could lead to a negative effect on the function of the hydraulic valve as well as components running downstream through their target service life.
Furthermore, the filtration efficiency of the sieve filter is dependent on its mesh width or the size of the passage openings. In this respect, the penetration of external sediment particles into the hydraulic valve is merely limited but not completely prevented. This limitation is especially disadvantageous for hydraulic valve constructions, in which the hydraulic valve carries a flow of hydraulic medium coming from several connection lines. For example, in a 3/2 directional control valve, for achieving the (limited) effect, it would be necessary to provide at least both the pressure connection P and also the work connection A with a filter element, because in a second switch position of such a hydraulic valve, the hydraulic medium would flow out of the work line A coming in the direction of the tank connection T. The installation of a second filter element, however, is associated with correspondingly high and cost-intensive structural expense.
In addition, for retaining very small particles, a fine or very fine filter has to be provided, which generates, however, an undesirably high pressure loss in the hydraulic medium at the inlet and, in the case of the previously mentioned 3/2 directional control valve with two filter elements, also at the outlet from the hydraulic valve. This pressure loss also increases with the loading of the filter with sediment particles over the course of time.